> Why timestamp?
> What happens if time on server is changed?
> How do you sinc the servers?
>

I agree - there should never be a PK collision (or threat of one) in a good
replication system.
You are suggesting the use of two fields to do the work - what's wrong with
each database having an installation number. A table with one value,
installation one to 100 or whatever.
One generator per table for one field with full integer scope (even 64bit
integer)
And the other field being installation number which is inserted by trigger
on every record insert. You can use the single PH field for local work and
the replation service uses the twin field PK for replication.
As I remember, there was a long discussion about this quite a while ago and
this seemed to me to be the most respected solution.
Alan